c - How to loop through a va_list if the number of arguments is unknown? -

how loop through va_list if number of additional arguments unknown?

#include <stdio.h> #include <stdarg.h>  int add(int x, int y, ...) {     va_list intargs;     int temp = 0;      va_start(intargs, y);     int i;     (i = 0; < 3; i++) { /* how can loop through number of args? */          temp += va_arg(intargs, int);     }     va_end(intargs);      return temp + x + y; }  int main() {     printf("the total %d.\n", add(1, 2, 3, 4, 5));     return 0; } 

use sentinel value terminator, e.g null or -1